The present invention generally relates to an automatic chemical analysis, and more particularly to a system for managing liquids such as reagents and buffer solution for use in an automatic chemical analyzer.
In an automatic chemical analyzer, one or more reagents are added to a sample liquid to effect a reaction and a reacted solution is tested by a colorimeter or an ion sensitive electrode device. At present, in accordance with the technological progress of analyzer systems, it has been required to make an amount of a reagent as small as possible. For instance, in case of testing a serum, an amount of the sample serum for a single test item is about 5 to 25 .mu.l and an amount of a reagent is about 50 to 200 .mu.l . Further, in order to simplify the maintenance, the reagent is stored in a refrigerator provided in the analyzer and can be kept therein for more than one week. In some analyzers, a reagent of high concentration is stored in a reagent tank and a diluted reagent is delivered into a reaction vessel. Then the number of tests which can be performed by the reagent contained in the tank can be increased by a factor which corresponds to a dilution ratio.
Formerly it was common to set required reagents in an analyzer at a start of analyzing work every day, but presently an exchange or supplement of reagents is effected once a week due to the fact that a required amount of the reagent has been decreased materially and the reagent has been hardly damaged for a long time. Then, there has arisen another problem that the management of the reagents might be forgotten by a user. In order to avoid such a problem, there has been proposed in Japanese patent application laid-open publication No. 82,769/82 an apparatus for managing reagents set in an automatic chemical analyzer. In this known apparatus residual amounts of reagents contained in reagent tanks are automatically calculated from signals supplied from a liquid level detector and signals representing distances over which a nozzle of a reagent pipetter descends in respective tanks, and calculated residual amounts of the reagents are displayed on a screen of a cathode ray tube. In this known reagent managing apparatus, in order to obtain a high reliability it is necessary to make high the precision of the liquid level detector and the mechanism for moving the nozzle up and down including, for instance a pulse motor. As a result, it is apparent that the liquid level detector and the reagent pipetter become complicated in construction and expensive in cost.